|
Index |
Item/Specification/Standard |
Notes/Comments |
| 1 |
MATERIALS |
|
| |
Specified properties of
all materials shall be verified by appropriate AASHTO or ASTM standard
tests either performed by the material supplier or the precast concrete
plant.
In order to establish evidence of
proper manufacture and conformance with plant standards and project
specifications, a system of records shall be maintained to provide full
information on material tests, mix designs, concrete tests, and any other
necessary information.
For control of concrete, testing of
specimens, and design and control of concrete mixes, each precast concrete
plant shall be equipped with adequate testing equipment and staffed with
personnel trained in its use.
If the plant has contracted for
quality control to be performed by an outside independent laboratory, the
laboratory shall be accredited by the Cement and Concrete Reference
Laboratory of the National Institute of Standards and Technology (National
Voluntary Laboratory Accreditation Program). The laboratory shall conform
to the requirements of ASTM E329 and the plant or independent laboratory
shall meet the concrete inspection and testing section requirements of
ASTM C1077. |
|
| |
Suppliers of materials
shall be required to furnish certified test reports for cement,
aggregates, admixtures, curing materials, reinforcing and prestressing
steel, and hardware materials, indicating that these materials comply with
the applicable AASHTO and ASTM standards, project specifications and plant
standards. |
|
| 1.1 |
Cement |
|
| |
Cement shall conform to
AASHTO M85.
If mill certificates are not
supplied, representative testing of each shipment of cement is required
before use. The mill certificate shall contain the alkali content in
percent expressed as Na2O equivalent. Mill certificates or test
reports of cement shall be kept on file in the plant for at least 5 years
after use. |
Mill test reports should
be reviewed for changes from previous reports. Lower concrete strength
should be expected from: lower cube strength; lower C3S; lower fineness;
higher % retained on No. 325 sieve (45 mm); and higher loss on ignition.
Increase in total alkali may reduce concrete strength gain after 7 days
and impair the strength-producing efficiency of water-reducing admixtures.
Variation in the color of gray cement may in part be traced to a variable
Fe2O3 content (a 2% variation in
Fe203 being significant). |
| 1.1.1 |
Type |
|
| |
Type shall be as
specified in the contract documents. If not specified Types I, II, III,
IV, or V may be used.
Each shipment shall be referenced to
a certified mill test report, indicating compliance with the specified
type and compliance with AASHTO M85. Test reports shall be on file with
the producer. |
|
| 1.1.2 |
Alkali
Content |
|
| |
If the aggregates used
result in mortar bar expansion greater than 0.20% at an age of 16 days
when tested in accordance with AASHTO T303, the equivalent alkali content
(Na2O + 0.658K2O) of the cement shall not exceed
0.60%. If the AASHTO T303 test results in 16 day mortar bar expansion
greater than 0.10% but less than 0.20% the equivalent alkali content of
the cement shall not exceed 0.60% unless additional testing or
examinations in accordance with ASTM C295 and ASTM C856 indicate that
reactive constituents are negligible. |
|
| 1.1.3 |
Fineness |
|
| |
Fineness of Type III
Portland Cement shall not exceed 5600 cm2/gm determined in
accordance with AASHTO Test Method T153. |
|
| 1.1.4 |
Blended Hydraulic
Cement |
|
| |
Blended
hydraulic cement shall conform to AASHTO M240.
AASHTO M85 (ASTM
C150) -- Standard Specification for Portland Cement
AASHTO M240 (ASTM C595) --
Blended Hydraulic Cement
AASHTO T106 (ASTM C109) -- Compressive
Strength of Hydraulic Cement Mortar
AASHTO T127 (ASTM C183) -- Sampling
and Amount of Testing of Hydraulic Cement
AASHTO T131 (ASTM C191) -- Time of
Setting of Hydraulic Cement by Vicat Needle
AASHTO T185 (ASTM C359) -- Early
Stiffening of Portland Cement (Mortar Method)
AASHTO T303 -- Rapid Identification of Alkali Silica Reaction
Products in Concrete
AASHTO T153
(ASTM C204) -- Standard Test Method for Fineness of
Hydraulic Cement by Air
Permeability Apparatus
ASTM C295 -- Petrographic Examination of Aggregates for
Concrete
ASTM C856 -- Petrographic Examination of Hardened
Concrete |
| 1.2 |
Aggregates |
|
| |
Sieve analysis, in
accordance with AASHTO T27, shall be conducted on samples taken from the
initial shipment received at the plant. Specific gravity, absorption, and
petrographic analysis tests performed within the past 5 years shall be
obtained from the supplier prior to the time of first usage or when a new
lift or horizon in a quarry is utilized or there appears to be a change in
quality of the aggregate.
Tests for deleterious substances and
organic impurities shall be done at the start of a new aggregate supply
and annually thereafter, unless problems are encountered requiring more
frequent testing. |
|
| 1.2.1 |
Alkali-Silica
Reaction |
|
| |
Evaluation of aggregates
for potential alkali-silica or alkali-carbonate reactions (excessive
expansion, cracking, or popouts in concrete) shall be based on at least 15
years of exposure to moist conditions of structures made with the
aggregate in question, if available, or petrographic examination (ASTM
C295) to characterize aggregates and determine the presence of potentially
reactive components. |
|
| 1.2.2 |
Petrography |
|
| |
If an aggregate is found
to be susceptible to alkali-silica reaction using ASTM C295, it shall be
evaluated further using ASTM C1260 and CSA A23.2-14A. Aggregates which
exhibit ASTM C1260 mean mortar bar expansion at 14 days greater than 0.10
percent shall be considered potentially reactive. Aggregates further
evaluated by CSA A23.2-14A that exhibit mean concrete prism expansion at
one year greater than 0.04 percent shall be considered potentially
reactive. Aggregate sources exhibiting expansions no more than 0.04
percent and demonstrating no prior evidence of reactivity in the field
shall be considered non-reactive. Reliance shall not be placed on results
of only one kind of test in any evaluation.
If an aggregate is judged to be
susceptible to alkali-carbonate reaction using ASTM C295, it shall be
evaluated further for alkali-carbonate reaction in accordance with ASTM
C586 or ASTM C1105. |
|
| 1.3 |
Coarse
Aggregate |
|
| |
Coarse aggregates, other
than lightweight aggregates, shall conform to the requirements of AASHTO
M80.
The maximum size of coarse aggregate
shall not exceed:
1. One third of the minimum section
thickness.
2. Three-fourths of the minimum
clear depth of cover.
3. Two-thirds of the spacing between
individual reinforcing bars or bundles of bars or pretensioning tendons or
post-tensioning ducts.
Coarse aggregates shall be obtained
from sources from which representative samples have been subjected to all
tests prescribed in the governing specifications. |
|
| 1.3.1 |
Gradation |
|
| |
A sieve analysis (AASHTO
T27) and unit weight test (ASTM C29) shall be conducted in the plant with
test samples taken at any point between stockpile and batching hopper for
aggregate being used. Such tests shall be carried out for each aggregate
type and size in use at least once every week or for each 1,000 tons where
usage in a one-week period exceeds such volume. |
|
| 1.3.2 |
Moisture
Content |
|
| |
|
|
| 1.4 |
Fine
Aggregate |
|
| |
Fine aggregates shall
comply with AASHTO M6 or applicable specified requirements. Variations in
fineness modulus of fine aggregates shall not exceed _0.20 from the value
used for the mix design and the amount retained on any two consecutive
sieves shall not change by more than 10 percent by weight of the total
fine aggregate sample. |
|
| 1.4.1 |
Materials |
|
| |
Fine aggregates for
concrete mixes, other than lightweight aggregates, shall consist of high
quality natural sand or sand manufactured from coarse aggregate. |
|
| 1.4.2 |
Gradation |
|
| |
A sieve analysis (AASHTO
T27) and unit weight test (ASTM C29) shall be conducted in the plant with
test samples taken at any point between stockpile and batching hopper for
aggregate being used. Such tests shall be carried out for each aggregate
type and size in use at least once every week or for each 500 tons where
usage in a one-week period exceeds such volume. |
|
| 1.4.3 |
Moisture
Content |
|
| |
|
|
| 1.5 |
Lightweight
Aggregate |
|
| |
Tests for gradation,
unit weight and impurities shall be made in accordance with requirements
of AASHTO M195. |
|
| 1.5.1 |
Materials |
|
| |
Lightweight aggregates
shall conform to the requirements of AASHTO M195 (ASTM
C330). |
|
| 1.5.2 |
Specific
Gravity |
|
| |
The specific gravity of
lightweight aggregate shall be determined in accordance with procedures
described in ACI 211.2, Appendix A C Pycnometer Method. The oven-dry loose
unit weight (ASTM C29) of the lightweight aggregate shall be determined. A
maximum 10 percent change in unit weight of successive shipments from a
sample submitted for acceptance tests is allowed. |
|
| 1.5.3 |
Moisture
Content |
|
| |
AASHTO M80
-- Coarse Aggregate for Portland Cement Concrete
ASTM C33 --
Standard Specification for Concrete Aggregates
AASHTO M6 -- Fine Aggregate for
Portland Cement Concrete
AASHTO M43 -- Sizes of Aggregate for Road and Bridge
Construction
AASHTO M195 (ASTM C330) -- Lightweight Aggregates for
Structural Concrete
AASHTO T2 (ASTM D75)AASHTO T11
(ASTM C117) -- Sampling of AggregatesMaterials Finer Than 75-?m (No.
200) Sieve in
Mineral Aggregates by Washing Unit Weight and Voids in
Aggregate
AASHTO
T19 (ASTM C29) -- Organic Impurities in Fine Aggregates for
Concrete
AASHTO
T21 (ASTM C40) -- Sieve Analysis of Fine and Coarse
Aggregate
AASHTO
T27 (ASTM C136) -- Specific Gravity and Absorption of Fine
Aggregate
AASHTO
T84 (ASTM C128) -- Specific Gravity and Absorption of Coarse
Aggregate
AASHTO
T85 (ASTM C127) -- Total Moisture Content of Aggregate by
Drying
AASHTO T255
(ASTM C566) -- Accelerated Detection of Potentially
Deleterious
AASHTO T303 -- Expansion of Mortar Bars Due to
Alkali-Silica Reaction
Petrographic Examination of Aggregates for Concrete
Potential Alkali Reactivity of
Carbonate Rocks for
ASTM C295 -- Concrete Aggregates (Rock Cylinder
Method)
ASTM C586
-- Length Change of Concrete Due To Alkali-Carbonate Rock
Reaction
ASTM
C1105 -- Potential Alkali Reactivity of Aggregates (Mortar Bar
Method)
ASTM C1260
-- Methods of Test for Concrete
CSA A23.2
|
| 1.6 |
Water |
|
| |
Water shall be free from
deleterious matter that may interfere with the setting time or strength of
the concrete.
Water, either potable or
non-potable, shall be free from injurious amounts of oils, acids, alkalis,
salts, organic materials, chloride ions or other substances that may be
deleterious to concrete or steel.
Water shall not exceed the maximum
concentration limits given in Table 1.6.
Water shall be potable or chemically
analyzed when a private well or non-potable water is used in the concrete
mix. Except for water from a municipal supply, an analysis of the water
shall be on file at the plant, updated annually, and clearly related to
the water in use. Seawater shall not be used.
Mortar cubes made in accordance with
AASHTO T106 using nonpotable or questionable mixing water shall have 7-day
strengths equal to at least 90 percent of the strengths of companion
specimens made with potable or distilled water. Time of set (AASHTO T131)
for mortar made with questionable water may vary from one hour earlier to
1-1/2 hours later than the control sample made with potable or distilled
water. Water resulting in greater variations shall not be
used. |
Excessive impurities may
cause efflorescence, staining, increased volume change and reduce
durability. Therefore, limits should be set on chlorides, sulfates,
alkalis and solids in the mixing water. Some impurities may have little
effect on strength and setting time, yet they can adversely affect
durability and other properties. The chloride ion content should be
limited to a level well below the recommended maximum, if practical.
Chloride ions contained in the aggregates and in admixtures should be
considered in evaluating the acceptability of total chloride ion content
of mixing water. |
|
Table
1.6 |
|
| 1.7 |
Mineral
Admixtures |
|
| |
Mineral admixtures or
pozzolans meeting AASHTO M295 or ASTM C1240 may be added for additional
workability, increased strength and reduced permeability and
efflorescence. If a HRWR is used with silica fume, ensure that the
admixture to be used is compatible with that already in the silica fume if
any. The amount of silica fume or metakaolin in concrete shall not exceed
10 percent by weightof the portland cement unless evidence is available
indicating that the concrete produced with a larger amount will have
satisfactory strength, durability, and volume stability. |
|
| 1.7.1 |
Fly Ash |
|
| |
Fly ash or other
pozzolans used as admixtures shall conform to AASHTO M295 |
|
| 1.7.2 |
Silica
Fume |
|
| |
Silica fume shall
conform to ASTM C1240. |
|
| 1.7.3 |
Blast Furnace
Slag |
|
| |
|
|
| 1.7.4 |
Metakaolin |
|
| |
Metakaolin
shall conform to ASTM C618 Class N requirements. AASHTO
M295 (ASTM C618) - Coal Fly Ash and Raw or Calcinated Natural
Pozzolan for Use as a Mineral Admixture in Concrete
AASHTO M302 (ASTM C989) - Ground
Granulated Blast-Furnace Slag for Use in Concrete and Mortars
AASHTO M307 - Microsilica
for Use in Concrete and Mortar
ASTM C311 - Sampling and Testing
Fly Ash or Natural Pozzolans for Use as a Mineral Admixture in Portland
Cement Concrete
ASTM C1240 - Silica Fume for Use as a Mineral Admixture
in Hydraulic-Cement Concrete, Mortar, and Grout |
| 1.8 |
Chemical
Admixtures |
|
| |
If a satisfactory
history of admixture performance with the specific concrete materials to
be used in a project is not available, a trial mixture program with those
materials, particularly the cement, shall be conducted. The trial mixture
program shall demonstrate satisfactory performance of the admixture
relative to slump, workability, air content, finishability and strength
under the conditions of use, particularly with respect to temperature and
humidity. Admixtures shall be carefully checked for compatibility with the
cement or other admixtures used to ensure that each performs as required
without affecting the performance of the other admixtures. Admixture
supplier's recommendations shall be observed subject to plant checking and
experience. The affect of variations in dosage and the sequence of
charging the admixtures into the mixer shall be determined from the
recommendations of the admixture supplier or by trial mixes. |
All types of admixtures
used should be materials of standard manufacturing having well established
records of tests to confirm their properties. Expected performance of a
given brand, class, or type of admixture may be projected from one or more
of the following sources:
1. Results from jobs which have used
the admixture under good technical control, preferably using the same
materials and under conditions similar to those to be expected.
2. Technical literature and
information from the manufacturer of the admixture.
3. Laboratory tests made to evaluate
the admixture.
Trial mixtures can be made at
midrange slump and air contents expected or specified for the project. The
cement content or water/cement ratio should be that required for the
specified design strength and durability requirements for the job. Trial
mixtures also can be made with a range of cement contents, water/cement
ratios, slumps or other properties to bracket the project requirements. In
this manner, the optimum mixture proportions can be selected and the
required results achieved.
Various results can be expected with
a given admixture due to differences in dosage, cement composition and
fineness, cement content, aggregate size and gradation, the presence or
other admixtures, addition sequence, changes in water/cement ratio and
weather conditions from day to day.
Differences in setting times and
early strength development also can be expected with different types and
sources of cement as well as concrete and ambient
temperatures. |
| |
The manufacturer of the
admixture shall certify that individual lots meet the appropriate AASHTO
and ASTM requirements. All relevant admixture information with respect to
performance, dosages, and application methods and limitations shall be on
file at the plant. Other admixtures shall conform to the requirements of
ASTM C494, Types A, B, D, F, and G, or ASTM C1017. The supplier shall
certify these admixtures do not contain calcium chloride.
Laboratory test reports submitted by
the supplier of chemical admixtures shall include information on the
chloride ion content and alkali content expressed as Na2O
equivalent. Test reports are not required for air-entraining admixtures
used at dosages less than 2 fl oz per 100 lb (130 ml per 100 kg) of cement
or nonchloride chemical admixtures used at maximum dosages less than 5 fl
oz per 100 lb (325 ml per 100 kg). Both the chloride ion and total alkali
content of the admixture are to be expressed in percent by mass of cement
for a stated or typical dosage of the admixture, generally in fluid ounces
per 100 lb of cement or (milliliters per 100 kg). |
|
| |
Calcium chloride or
admixtures containing chloride ions (Cl-1) from other than
impurities from admixture ingredients shall not be used in prestressed
concrete, as their use will produce deleterious concentrations of chloride
ions in the mixing water and cause corrosion. |
|
| 1.8.1 |
Air
Entraining |
|
| |
Air entraining
admixtures shall conform to the requirements of ASTM C260. |
The use of air
entrainment is recommended to enhance durability when concrete will be
subjected to freezing and thawing when wet. |
| 1.8.2 |
Water
Reducing |
|
| |
Water reducing,
retarding or accelerating admixtures shall conform to the requirements of
ASTM C494. |
|
| 1.8.3 |
Retarding |
|
| |
|
|
| 1.8.4 |
WR &
Retarding |
|
| |
|
|
| 1.8.5 |
HRWR |
|
| |
High-range
water-reducing admixtures (HRWR) or (superplasticizers) shall conform to
the requirements of ASTM C494 Type F or G. |
|
| 1.8.6 |
HRWR &
Retarding |
|
| |
AASHTO M194 (ASTM
C494) -- Chemical Admixtures for Concrete
ASHTO M154 (ASTM C260) --
Air-Entraining Admixtures for Concrete |
| 1.9 |
Reinforcement |
|
| |
Plant testing of
reinforcing steel, welded wire reinforcements, or prestressing materials
shall not be required if mill certificates and coating reports are
supplied. Mill certificates for reinforcing steel, welded-wire
reinforcement, and prestressing materials in stock or in use shall be
required and indicate that the material meets the requirements of
applicable AASHTO and ASTM specifications.
Certificates shall be obtained for
each size and shipment and for each grade of steel.
Mill certificates for all
reinforcing materials shall be kept on file at the plant for at least five
years after use. Incoming steel, wire, and strand shall be examined for
damage, excessive scaling, or pitting. |
|
| 1.10 |
Steel
Reinforcement |
|
| |
Steel reinforcing bars
shall be deformed bars of the designated types of steel, sizes and grades
and shall conform to the applicable specifications as shown on the
production drawings. |
|
| |
When it is required to
restrict the range in the chemical composition of steel to provide
satisfactory weldability, the supplier shall certify conformance with
these supplemental requirements in writing.
In lieu of mill certificates,
reinforcing steel shall be tested for its physical and chemical properties
in accordance with ASTM A370 to verify conformance with the applicable
specifications. |
|
| |
It shall be permissible
to substitute:
- a metric size bar of Grade 300
for the corresponding inch-pound size bar of Grade 40;
- a metric bar of Grade 350 for the
corresponding inch-pound size bar of Grade 60;
- and a metric size bar of Grade
520 for the corresponding inch-pound size bar of Grade 75.
|
|
| |
Reinforcement with rust,
seams, surface irregularities, or mill scale shall be considered as
satisfactory, provided the minimum nominal dimensions, including minimum
average height of deformations, and nominal weight of a hand-wire-brush
test specimen are not less than the applicable ASTM specification
requirements. |
|
| 1.10.1 |
Galvanized |
|
| |
Zinc-coated (galvanized)
reinforcement shall conform to ASTM A767/A767M and be chromate
treated. |
Where galvanizing of
reinforcing bars is required, galvanizing is usually performed after
fabrication. The ASTM A767/A767M specification prescribes minimum
finished bend diameters for bars that are fabricated before galvanizing.
Smaller finished bend diameters are permitted if the bars are
stress-relieved. The ASTM A767/A767M specification has two classes of zinc
coating weights. Class II 2.0 oz/ft2 (610g/m2) is
normally specified for precast concrete units. |
| 1.10.2 |
Epoxy
Coated |
|
| |
Epoxy-coated
reinforcement shall conform to ASTM A775/A775M or A934/A934M. Any plant
supplying epoxy-coated reinforcement shall be a participant in the CRSI
Voluntary Certification Program for Fusion-Bonded Epoxy Coating Applicator
Plants. Fading of the epoxy coating color shall not be cause for rejection
of epoxy coated reinforcing bars. |
When epoxy-coated
reinforcing bars are exposed to sunlight over a period of time, fading of
the color of some epoxy coatings may occur. Since the discoloration does
not harm the coating nor affect its corrosion protection properties, such
fading should not be the cause for rejection of the coated
bars. |
| 1.10.3 |
Welded Wire
Fabric |
|
| |
Welded wire
reinforcement shall conform to the following applicable
specifications:
- Plain Wire ASTM A82
- Deformed Wire ASTM A496
- Welded Plain Wire Reinforcement
ASTM A185
- Welded Deformed Wire
Reinforcement ASTM A497
|
|
| |
The in-plant review and
monitoring of welded-wire reinforcement shall include a periodic
inspection as the material is received to confirm that the styles conform
to the required size and spacing specified. Spacing of the wires shall be
within 1/4 inch (6 mm) of the desired spacing, and the resistance welds at
intersections of wires shall have not more than 1 percent broken welds.
Additionally, if specific finish requirements are specified, such as
galvanizing or epoxy coating, this shall be confirmed at the point of
delivery.
Galvanized welded wire reinforcement
shall be made from zinc-coated (galvanized) carbon steel wire conforming
to ASTM A641; or be hot-dipped galvanized and be chromate treated; or be
allowed to weather. Epoxy-coated welded wire reinforcement shall conform
to ASTM A884/A884M, Class A. All damaged areas of epoxy coating shall be
repaired (touched-up) with epoxypatching material.
Welded wire reinforcement mesh
spacing and wire sizes (gages) shall be shown on the production
drawings.
AASHTO
M31 (ASTM A615) - Deformed and Plain Billet-Steel Bars for
Concrete Reinforcement
AASHTO M32 (ASTM A82) - Plain Steel Wire for Concrete Reinforcement
AASHTO M54 (ASTM A184) - Fabricated Deformed Steel Bar
Mats for Concrete Reinforcement
AASHTO M55 (ASTM A185) - Plain
Steel Welded Wire Fabric for Concrete Reinforcement
AASHTO M221 (ASTM A497) - Deformed
Steel Welded Wire Fabric for Concrete Reinforcement
AASHTO M225 (ASTM
A496) - Deformed Steel Wire for Concrete Reinforcement
AASHTO M284 (ASTM
D3963) - Epoxy Coated Reinforcing Bars
ASTM A706 - Specification for
Low-Alloy Steel Deformed and Plain Bars for Concrete Reinforcement |
|
| 1.11 |
Prestressing
Strand |
|
| |
Strand materials for
prestressing shall consist of:
a. uncoated, low
relaxation wire strand conforming to AASHTO M203, Grade 270
1860,
b. uncoated,
stress relieved (normal relaxation) strand, conforming to AASHTO M203,
Grade 270 1860. |
|
| |
Mill certificates from
suppliers shall be on file at plant offices for tendon materials in
current use. Certificates shall be obtained and kept on file for each ten
reels or coils of prestressing strand or wire in each size, and for each
heat or at least for each shipment if less than ten reels or coils.
The stress-strain curve of the
prestressing steel shall be on record. Stress-strain curves shall be for
material tested from heats used to produce reel packs and shall be
referenced to those reel packs. Average, typical or generic curves are not
acceptable.
The capability of the strand to
properly develop bond shall either be substantiated by certification from
the strand supplier or by testing. |
|
| |
A light bond coating of
tight surface rust on prestressing tendons is permissible, provided strand
surface shows no pits visible to the unaided eye after rust is removed
with a non-metallic pad. |
Due to bond development
required of concrete to prestressing strand, bars, or wires, the surface
condition of tendons is critical to prestressed concrete. The presence of
a light rust on a strand has proven to be an enhancement to bond over
bright strand and therefore should not be a deterrent to the use of the
strand. A pit visible to the unaided eye, when examined as described in
AEvaluation of Degree of Rusting on Prestressed Concrete Strand@, Sason,
Augusto S., PCI Journal, May-June 1992, V.37, No. 3 pp. 25-30 is cause for
rejection. A pit of this magnitude is a stress raiser and greatly reduces
the capacity of the strand to withstand repeated or fatigue loading. In
many cases, a heavily rusted strand with relatively large pits will still
test to an ultimate strength greater than specification requirements.
However, it will not meet the fatigue test requirements. |
| |
AASHTO M203 (ASTM
A416) -- Uncoated Seven-Wire Steel Strand for Concrete
Reinforcement
AASHTO M204 (ASTM A421) -- Uncoated Stress-Relieved Steel
Wire for Prestressed Concrete |
| 1.12 |
Pre-Tensioning |
|
| |
Strand chucks for
pre-tensioning shall be capable of anchoring the strand without slippage
after seating. Length of grips and configuration of serrations shall be
such as to ensure against strand failure within the vise jaws at stresses
less than 95 percent of strand ultimate strength. Steel casings for strand
vises shall be verified by the manufacturer as capable of holding at least
100 percent of the ultimate strength of the strand. |
|
| |
Devices used to deflect
the strand to the required position shall be designed to minimize friction
to the level consistent with the tolerances for strand tensioning. Strand
shall be able to move freely over, under, or through the device. |
Harped strands must be
held in position by devices capable of supporting the load imparted from
the tensioned strand without excessive deformation. Excessive friction in
such devices can cause the strand tension to vary over the length of the
bed. If a strand becomes Apinched@ or otherwise caught in the device,
strand breakage can occur.
Strand restraining devices should be
designed for an appropriate factor of safety. |
| 1.13 |
Post-Tensioning |
|
| |
|
|
| 1.13.1 |
Bars |
|
| |
AASHTO M275
(ASTM A772) |
Uncoated
High-Strength Steel Bar for Prestressing Concrete |
| 1.13.2 |
Anchors |
|
| |
A tendon anchorage for
post-tensioning shall meet the following requirements:
1. An anchorage for
bonded tendons tested in an unbonded state shall develop 95 percent of
the actual ultimate strength of the prestressing steel, without
exceeding anticipated set attime of anchorage. An anchorage which
develop less than 100 percent of the minimum specified ultimate strength
shall be used only where the bond length provided is equal to or greater
than the bond length required to develop 100 percent of the minimum
specified ultimate strength of the tendon. The required bond length
between the anchorage and the zonewhere the full prestressing force is
required under service and ultimate loads shall be sufficient to develop
the specified ultimate strength of the prestressing steel. Determine the
bond length by testing a full-sized tendon. If in the unbonded state the
anchorage develops 100 percent of the minimum specified strength it need
not be tested in the bonded state.
2. An anchorage for unbonded
tendons shall develop 95 percent of the minimum specified ultimate
strength of the prestressing steel with an amount of permanent
deformation that will not decrease the expected ultimate strength of the
assembly.
3. The minimum elongation of a
strand under load in an anchorage assembly tested in the unbonded state
shall be not less than 2 percent when measured in a gauge length of
10-ft. (3 m).
Anchorage castings shall be nonporous and free of sand,
blow-holes, voids and other defects. For a wedge type anchorage, the wedge
grippers shall be designed to preclude premature failure of the
prestressing steel due to notch or pinching effects under static test load
conditions to determine yield strength, ultimate strength and elongation
of the tendon.
An anchorage of any type may be used
provided the basic requirements noted herein are demonstrated by an
acceptable test program. |
|
| 1.13.3 |
Duct |
|
| |
Sheathing for bonded
post-tensioned tendons shall be strong enough to retain its shape, resist
unrepairable damage during production, and prevent the entrance of cement
paste or water from the concrete. Sheathing material left in place shall
not cause harmful electrolytic action or deteriorate. The inside diameter
shall be at least 1/4 in. (6 mm) larger than the nominal diameter of
single wire, bar or strand tendons; or in the case of multiple wire, bar
or strand tendons, the inside cross-sectional area of the sheath shall be
at least twice the net area of the prestressing steel. Sheaths shall be
capable of transmitting forces from the grout to the surrounding concrete.
Sheaths shall have grout holes or vents at each end and at all high points
except where the degree of tendon curvature is small and the tendon is
relatively level. |
The void in the concrete
in which the tendon is to be located may also be formed with inflatable
and removable tubes. the tendon is subsequently pulled through and no
additional sheathing is required. |
| |
Sheathing for unbonded
tendons (monostrand post-tensioning system) shall be polypropylene,
high-density polyethylene or other plastic which is not reactive with
concrete, coating or steel. The material shall be waterproof and have
sufficient strength and durability to resist damage and deterioration
during fabrication, transport, storage, installation, concreting and
tensioning. The sheath shall have a coefficient of friction with the
strand of less than 0.05. Tendon covering shall be continuous over the
unbonded length of the tendon and shall prevent the intrusion of water or
cement paste and the loss of the coating material during concrete
placement. The sheaths shall not become brittle or soften over the
anticipated exposure temperature and service life of the structure. The
minimum wall thickness of sheaths for non-corrosive conditions shall be
0.04 in (1 mm). The sheathing shall have an inside diameter at least 0.030
in (0.76 mm) greater than the maximum diameter of the strand.
Tendons shall be lubricated and
protected against corrosion by a properly applied coating of grease or
other approved material. Minimum weight of coating material on the
prestressing strand shall be not less than 2.5 pounds (1.1 kg) of coating
material per 100 ft. (30.5 m) of 0.5 in. (12 mm) diameter strand,
and 3.0 pounds (1.4 g) of coating material per 100 ft. (30.5 m) of 0.6 in
(15.24 mm) diameter strand. The amount of coating material used shall be
sufficient to ensure essentially complete filling of the annular space
between the strand and the sheathing. The coating shall extend over the
entire tendon length. Coatings shall remain ductile and free from cracks
at the lowest anticipated temperature and shall not flow out from the
sheath at the maximum anticipated temperature. Coatings shall be
chemically stable and non-reactive to the tendon, the concrete and the
sheath. |
|
| 1.13.4 |
Grout |
|
| |
Grout for bonded tendons
shall consist of a mixture of cement and water unless the gross inside
cross-sectional area of the sheath exceeds four times the tendon
cross-sectional area, in which case a fine aggregate may be added to the
mixture. Fly ash and pozzolanic mineral admixtures may be added at a ratio
not to exceed 0.30 by weight of cement. Mineral admixtures shall conform
to ASTM C618. Approved shrinkage-compensating material, which is well
dispersed through the other admixture, may be used to obtain 5 to 10
percent unrestrained expansion of the grout. Admixtures containing more
than trace amounts of chlorides, fluorides, zinc or nitrates shall not be
used. Fine aggregate, if used, shall conform to ASTM C404, Size No. 2,
except that all material shall pass the No. 16 sieve. Grout shall achieve
a minimum compressive strength of 2,500 p.s.i. (17.2 MPa) at 7 days and
5,000 p.s.i. (34.5 MPa) at 28 days when tested in accordance with ASTM
C1107, and have a consistency that will facilitate placement. Water
content shall be the minimum necessary for proper placement, and the
water-cementitious materials ratio shall not exceed 0.45 by
weight. |
|
| |
AASHTO T106 (ASTM
C109) -- Compressive Strength of Hydraulic Cement Mortar
ASTM C1107 -- Packaged
Dry Hydraulic Cement Grout |
| 1.14 |
Steel
Assemblies |
|
| |
Random sampling shall be
done for each production lot of assemblies. Any failure of the visual
inspection or bend test shall require like testing on a random 10 percent
sample of the production lot. Any failure within this 10 percent sample
shall require inspection and bend testing of 100 percent of the production
lot, or replacement of the entire lot.
Substitution of reinforcing bars for
deformed bar anchors shall not be allowed unless approved by the
engineer.
Weld size and location shall be
checked for welded assemblies at a rate of one per 50 assemblies. If
discrepancies are found, then all assemblies shall be
checked. |
|
| 1.14.1 |
Stud
Anchors |
|
| |
Headed stud and deformed
bar anchor materials and base metal materials shall be compatible with the
stud welding process. Suppliers of both materials shall provide physical
and chemical certification on the products supplied. The tests shall
correlate to the material supplied. One unit for each 50 assemblies
received shall be selected and the stud weld(s) visually inspected, and
one stud bend tested, in accordance with the following
procedures. |
|
| |
The stud-welding
operator shall be responsible for the following tests and inspections to
ensure that the proper setup variables are being used for the weld
position, stud diameter, and stud style being welded. Testing is required
for the first two studs in each day's production and any change in the
setup such as changing of any one of the following: stud gun, stud welding
equipment, stud diameter, gun lift and plunge, total welding lead length,
or changes greater than 5 percent in current (amperage) and dwell
time.
Down-Hand Stud Welding
Qualifications
For studs welded in the down-hand
position, at the start of each production period, the operator shall weld
two studs of each size and type to a production weld plate or a piece of
material similar in material composition to the weld plate and within "25
percent of the production weld plate thickness. The test weld plate and
production weld plate pieces shall be clean of any dirt, paint,
galvanizing, heavy rust, or other coatings that could prevent successful
welding or adversely affect weld quality. These studs shall be visually
inspected by the operator to see whether a proper weld fillet has formed.
The weld fillet (flash) may be irregular in height or width, but shall
completely Awet@ the stud circumference without any visual sign of weld
undercut.
The test studs shall exhibit an
after weld length measurement shorter than the before weld stud length.
After weld length shall be consistent on both test welds and on all
production welds. Typical length reductions for various stud diameters are
as follows:
| Stud
Diameter, in. (mm) |
Length Reduction, in.
(mm) |
| 3/16 (5) through 1/2
(12) |
1/8 (3) |
| 5/8 (16) through 7/8
(22) |
3/16 (5) |
| 1 (25) and over |
3/16 to 1/4 (5 to
6) |
Records of stud welding shall be
maintained on an hourly basis, and be on file at the precast
plant. |
|
| |
AASHTO M102 (ASTM
A668) Carbon and Alloy Steel Forgings for General Industrial
Use
AASHTO M103 (ASTM
A27) Carbon Steel Castings for General Application
AASHTO M111 (ASTM A123) Zinc (Hot-Dip Galvanized) Coatings
on Iron and Steel Products
AASHTO M160 (ASTM A6) General
Requirements for Rolled Steel Plates, Shapes, Sheet Piling and
Bars for Structural Use
AASHTO M164 (ASTM A325) High Strength Bolts for Structural
Steel Joints
AASHTO M183 (ASTM A36) Structural Steel
AASHTO M232 (ASTM
A153) Zinc Coating (Hot-Dip) on Iron and Steel Hardware
AASHTO M253 (ASTM
A490) Heat-Treated Steel Structural Bolts, 150 ksi Minimum
Tensile Strength
AASHTO M291 (ASTM
A563) Carbon and Alloy Steel Nuts
AASHTO M298 (ASTM
B695) Coatings of Zinc Mechanically Deposited on Iron and
Steel
AASHTO M299 (ASTM
B696) Coatings of Cadmium Mechanically Deposited
AASHTO M300
Inorganic Zinc Rich Primer
AASHTO M314 Steel Anchor Bolts |
| 1.14 |
Manufactured Hardware
and Threaded Inserts |
|
| |
Plant tests shall not be
required for hardware but certification shall be obtained for all steel
materials and each different grade of steel to verify compliance with
specifications. Inserts need not be plant tested if used only as
recommended by the suppliers and within their stated (certified)
capacities and application qualifications. Records shall be on file
establishing working capacity of each kind and size of insert used for
handling and/or connection corresponding to the actual concrete strengths
when inserts are used, unless the manufacturer=s load table indicates
adequate capacity at a concrete strength lower than the maximum strength
at time of use. No extrapolation of the suppliers test data is permitted.
In lieu of certification for hardware, six specimens of each size and
material heat number of a steel item shall be tested in accordance with
ASTM A370 to verify conformance with the applicable ASTM specification.
For other hardware items information shall be on file at the plant
describing the material, and its qualities and applications, including
limitations. |
|
| 1.15 |
Bearings |
|
| |
|
|
| 1.15.1 |
Elastomeric
Pads |
|
| |
|
|
| 1.15.2 |
Assemblies |
|
| |
|
|
| 1.16 |
Grout and
Mortar |
|
| |
|
|
| 1.17 |
Epoxy |
|
| |
AASHTO
M200 |
Epoxy Protective
Coatings |
| 1.17.1 |
Epoxy
Mortar |
|
| |
|
|
| 1.17.2 |
Epoxy for Crack
Repair |
|
| |
|
|
| |
AASHTO M235
(ASTM C881) |
Epoxy Resin
Adhesives |
| 1.18 |
Curing
Compound |
|
| |
AASHTO M148
(ASTM C309) |
Liquid
Membrane-Forming Compounds for Curing Concrete |
| 2 |
CONCRETE |
|
| |
|
|
| 2.1 |
W/CM
Ratio |
|
| |
Maximum
water-cementitious materials ratio (w/cm) shall be 0.40 by
weight. |
|
| 2.2 |
Minimum Cementitious
Materials Content |
|
| |
Minimum cement content
shall be 564 pounds per cubic yard.
When mineral admixtures are used,
the minimum total cementitious materials content shall be 611 pounds per
cubic yard. |
|
| 2.3 |
Strength |
|
| |
Minimum 28-day design
concrete strength shall be 6000 psi.
The age for determining design
strength (f=c) may be increased at the discretion of the
Engineer. |
At the Engineer's
discretion, concrete strength up to 8,000 psi at 28 days may be
specified. |
| 2.3.1 |
Prestress Transfer
Strength |
|
| |
The minimum concrete
strength at transfer of prestressing force shall be 4000 psi or as
determined by the following relationships, whichever is greater.
- where f'ci is the
required strength at transfer (psi) and fc is the maximum
compressive stress at transfer (psi), or
- where ft' is the
maximum tensile stress at transfer (psi) between the end of the member
and the transfer point, or
- where ft is the
maximum tensile stress at transfer (psi) except as defined by b)
above.
Where the
concrete strength at transfer of prestressing force is controlled by
tensile stresses, supplemental tensile reinforcement may be provided to
control the stress. In this case, reinforcement shall resist the total
tensile force and the transfer strength determined by the maximum
allowable compressive stress. |
|
| 2.4 |
Proportioning |
|
| |
Concrete mix proportions
shall be established under carefully controlled laboratory conditions. For
concrete mixes, representative cylinders shall be cast and cured under
plant production conditions to demonstrate the strength and weight of the
concrete produced. All concrete mixes shall be developed using the brand
and type of cement, the type and gradation of aggregates, and the type of
admixtures proposed for use in production mixes. If at any time these
variables are changed, the mix shall be reevaluated. This reevaluation may
include one or more of the following concrete properties: (1) air content
or durability, and (2) strength (selected tests at appropriate
ages). |
|
| 2.5 |
Mixing |
|
| |
|
|
| 2.6 |
Delivery |
|
| |
|
|
| 2.7 |
Placement |
|
| |
|
|
| 2.8 |
Consolidation |
|
| |
|
|
| 2.9 |
Sampling |
|
| |
|
|
| 2.10 |
Testing |
|
| |
Records of all concrete
mixes used in a plant and their respective test results shall be on
file.
b. Samples for testing shall be
obtained in accordance with AASHTO T141. |
|
| 2.10.1 |
Compression |
|
| |
In addition to the
28-day tests, compression tests shall be made at the time of stripping the
production unit from the mold to determine whether stripping strength
requirements have been met. |
|
| 2.10.1.1 |
Specimens |
|
| |
Standard test specimens
shall be 6 x 12-inch 150 x 300-mm or 4 x 8-inch 100 x 200-mm
cylinders. |
|
| 2.10.1.2 |
Handling &
Curing |
|
| |
Test specimens shall be
made and cured in accordance with AASHTO T126. |
|
| 2.10.1.3 |
Procedure |
|
| |
Specimens shall be
tested in accordance with AASHTO T22. Test specimens using 4-inch 100-mm
cylinders are permitted providing proper correlation data with the
standard 6 x 12-inch 150 x 300-mm test cylinder is available. |
|
| 2.10.2 |
Slump |
|
| |
Slump tests shall be
conducted in accordance with AASHTO T119. Tests shall be made on the first
concrete delivery, whenever compressive test specimens are made, and
whenever the consistency of the concrete appears to change
significantly. |
|
| 2.10.3 |
Air
Content |
|
| |
Air content shall be
measured in accordance with ASTM C173 or C231 as applicable. Tests shall
be made on the first concrete delivery and whenever compressive test
specimens are made. |
|
| 2.10.4 |
Unit
Weight |
|
| |
Unit weight shall be
tested in accordance with AASHTO T121 or ASTM C567. Unit weight of normal
weight concrete shall be tested once per week for each mix design in use.
Lightweight concrete shall be tested daily to confirm batching
consistency.
When the nominal fresh unit weight
varies from the design value by more than _2 pcf _32 kg/m3
for normal weight concrete or _2 percent for structural lightweight
concrete, batch adjustments shall be made. |
|
| 2.10.5 |
Temperature |
|
| |
Temperature
shall be tested in accordance with ASTM C1064. Test shall be conducted
whenever slump, air content tests or compressive test specimens
are made. AASHTO M205
(ASTM C470) Molds for Forming Concrete Test Cylinders Vertically
AASHTO T22 (ASTM C39) Compressive Strength of Cylindrical
Concrete Specimens
AASHTO T23 (ASTM C31) Making and
Curing Concrete Test Specimens in the Field
AASHTO T119 (ASTM C143) Slump
of Hydraulic Cement Concrete
AASHTO T121 (ASTM C138) Mass per Cubic Foot, Yield, and
Air Content (Gravimetric) of Concrete
AASHTO T126 (ASTM C192) Making
and Curing Concrete Test Specimens in the Laboratory
AASHTO T141 (ASTM C172) Sampling
Freshly Mixed Concrete
AASHTO T152 (ASTM C231) Air Content of Freshly Mixed Concrete
by the Pressure Method
AASHTO T196 (ASTM C173) Air Content
of Freshly Mixed Concrete by the Volumetric Method
ASTM C1064 Temperature
of Freshly Mixed Portland Cement Concrete |
| 2.11 |
Curing |
|
| 2.11.1 |
Standard |
|
| 2.11.2 |
Accelerated |
|
| 2.11.2.1 |
Moisture
Retention |
|
| 2.11.2.2 |
Temperature
Limits |
|
| 2.11.2.3 |
Initial
Set |
|
| 3 |
PROCESSES |
|
| 3.1 |
Placement of
Reinforcement |
|
| 3.1.1 |
Fastening |
|
| 3.2 |
Tensioning |
|
| 3.2.1 |
Equipment |
|
| 3.2.2 |
Initial |
|
| 3.2.3 |
Final |
|
| 3.2.3.1 |
Straight |
|
| 3.2.3.2 |
Harped |
|
| 3.2.4 |
De-Tensioning |
|
| 3.2.5 |
Post-Tensioning |
|
| 3.3 |
Forming |
|
| 3.4 |
Finishing |
|
| 3.5 |
Form
Removal |
|
| 3.6 |
Handling |
|
| 3.7 |
Storage |
|
| 4 |
PLANT |
|
| 4.1 |
Certification |
|
| 5 |
PERSONNEL |
|
| 5.1 |
Training/Certification |
|
| 6 |
TOLERANCES |
|
TRAINING
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